This project has as its overall goals the identification of the molecular pathogenesis of lymphoproliferative diseases and the development of objective criteria for lymphoma diagnosis and prognosis, using the specific molecular and immunohistochemical characteristics identified in different lymphoma subtypes. There are several ongoing studies within this project. These include studies of CDK inhibitors in lymphomas, studies focused on the molecular characterization of ALCL, and studies of the functional consequences of mutations that occur in the translocated myc gene in Burkitts lymphoma. Over the last year we have focused on investigating abnormalities of the CDK-I p27 in the non-Hodgkins lymphomas. We reported an inverse correlation between the levels of immunohistochemically detectable p27 and proliferation rate, in the majority of lymphoma subtypes, with the notable exception of mantle cell lymphomas. These lymphomas which are unique in that they express high levels of cyclin D1 as a result of the t(11;14) translocation, show little or no expression of p27 regardless of their proliferation rate. In pursuing this finding, we have found that the high levels of cyclin D1 in these lymphomas are responsible for binding and physically sequestering the p27 protein in the cell. As a result of its sequestration p27 protein is rendered non-functional and becomes immunohistochemically undetectable. This appears to be an important mechanism through which high levels of cyclin D1 exert its oncogenic effect.We have also continued our work investigating the origin of and molecular pathogenesis of ALCL. In the past year we have begun to use comparative gene expression analysis using cDNA microarrays to study these unusual lymhomas. We have identified several unique gene products using this approach. One such gene, clusterin, was exclusively expressed in all cases of ALCL, but was not identified in over 150 primary lymphomas of other subtypes. Clusterin has been implicated in cell aggregation and may be responsible for the unusual adhesive growth properties of this lymphoma. This study illustrates the feasibility of using gene expression arrays not only to identify biologically significant gene expression patterns in lymphomas, but also to accelerate the discovery of diagnostic markers in cancer, in general.In the last year, we have completed studies on the functional effects of tumor-associated mutations that we previously reported to occur in the c-myc coding region in 8q24 translocated lymphomas. We showed that contrary to the mutations that occur in myc box 1, which increase the transformation efficiency of the c-myc protein, presumably through disruption of protein phosphorylation sites, mutations that occur in myc box 2 interfere with the ability of the protein to promote apoptosis. Thus, these tumor-associated myc mutations can be selected for either through their ability to enhance the transforming potential of the protein, or by their ability to interfere with the apoptosis function of c-myc. - Human Tissues, Fluids, Cells, etc.